We will try to define the mechanisms and dietary factors involved in the control of plasma lipoprotein concentrations and the interaction of lipoproteins with the arterial wall. Emphasis will be focused on the protein moiety and phospholipids of low density lipoproteins in squirrel monkeys and rabbits with nutritionally induced hyperlipidemia. The synthesis and particularly the catabolism of low density lipoproteins will be followed in vivo and in vitro (in isolated, noncultured hepatocytes, intestinal mucosal cells, and smooth muscle cells, as well as in whole tissue homogenates). The effect of nutritionally induced hyperlipidemia and atherosclerosis on the uptake of lipoproteins and on the exchange, net uptake, and metabolism of phospholipids, particularly lysolecithin, by arterial and other tissues will be emphasized. We will focus on the effect of lysolecithin on the penetration or binding of low density lipoproteins to arterial constituents. We will continue to investigate the controls, including dietary controls, of hepatic secretion of cholesterol, phospholipids, and bile salts and of gallstone nucleation and assembly in squirrel monkeys.